It appears evident from the figure that AAIW variability in the ocean is larger than what can be expected from slow diffusive flow. To give an estimate of the scale on which the observed variability is occurring, Fig. 3 shows a histogram of the distance between successive float surfacing locations. Most floats travel some 10–40km between successive data transmissions, but there is also a considerable range of larger distances. Very large distances are produced by data transmission failures causing gaps in the time series. Assuming that about half the float movement is caused by drift at the surface and the other half by drift at the parking depth, the standard deviations of Fig. 2 indicate the degree of variability on space scales varying from 5km to about 100km and more.